1. Field of the Invention
The present invention relates to processes for making alcohols from olefins using a dual phase catalyst system and related compositions.
2. Description of the Related Art
Internal combustion engines are commonly used on mobile platforms, in remote areas or in lawn and garden tools. There are various types of internal combustion engines. Spark type engines compress volatile fuels, such as gasoline, before ignition. Compression type engines take in air and compress it to generate the heat necessary to ignite the fuel, such as diesel.
Although hydrocarbon fuels are the dominant energy resource for such engines, alcohols, especially methanol and ethanol, have been used as fuels. In the 1970s, gasohol, a blend of mostly gasoline with some ethanol, was introduced during the Arab oil embargo. The primary alcohol fuel currently is ethanol. Ethanol is generally blended into gasoline in various quantities, normally at 10%, which typically results in a higher octane rating than regular gasoline. E-85 fuel contains 85% ethanol and 15% gasoline and M-85 has 85% methanol and 15% gasoline. Unfortunately, at that time, many of the elastomeric engine seals, hoses and gasket components were designed only for gasoline or diesel and deteriorated with the use of ethanol. Furthermore, the engines had to be equipped with fluorinated elastomers to run ethanol-based fuels.
Further limitations exist with respect to the use of grain-based fuels. For example, grain ethanol is expensive to produce. Furthermore, producing sufficient quantities of grain ethanol to satisfy the needs of the transportation industry is not practical because food crops and feed crops are and have been diverted into fuel. In addition, both methanol and ethanol have relatively low energy contents when compared to gasoline on a volumetric basis. Methanol contains about 50,000 Btu's/gallon and ethanol contains about 76,000 Btu's/gallon while gasoline contains about 113,000 Btu's/gal.
Long chain alcohols are often used together with amines/anilines as inhibitors to prevent metal corrosion and rubber/plastics swellings caused by the ethanol fuels. These long chain alcohols, such as dodecanol, can also be used as emulsifying agents. Mixed low cost methanol and ethanol were used together with long chain alcohols to form alcohol blended diesels or used as emulsifying diesel adjustors. However, long chain alcohols are relatively expensive to produce. The methanol-based and ethanol-based diesels also suffer from the drawback that they need other additives, such as long chain alcohols, alkyl esters and fatty acids to maintain a minimum Cetane number above 40 and to assure the diesel burns efficiently.
Some time ago, lead was added to gasoline to boost its octane rating, thereby improving the antiknock properties of gasoline. Lead is being eliminated in most countries from gasoline for environmental reasons. In response to the need to phase out lead, gasoline sold in the United States and many other countries was blended with up to 15% volumes of methyl-tertiary-butyl-ether (MTBE), an oxygenate, in order to raise the octane rating and to reduce environmentally harmful exhaust emissions. The industry is replacing MTBE with the use of fermented grain ethanol, but as discussed above, producing the necessary quantities of grain ethanol to replace MTBE is problematic in specific regions.
Another additive that has been used in fuels is Methylcyclopentadienyl Manganese Tricarbonyl (MMT). MMT has been a controversial gasoline additive for many years. MMT is able to increase octane but it increases emissions, which may have an adverse effect on health and exhaust catalytic conversion systems.
In lieu of these questionable additives, alcohols, such as butanols, can be used as combustible neat fuels or an oxygenate fuel additives or constituents in various types of fuels. When used as an oxygenate fuel, the BTU content is closer to the energy content of gasoline than many of the methanol or ethanol based fuels, as shown in Table 1.
TABLE 1Properties of Butanols as compared to GasolineAir-EnergyFuelSpecificHeat ofFuelDensityRatioEnergyVaporizationRONMONGasoline3214.62.90.3691-99 81-89  Butanols29.211.13.30.4396-11078-99.5
Alcohols can be prepared from olefins. There are no particularly effective olefin hydration processes, however, in place to convert mixed olefins into alcohols, especially butenes into butanols.
Hydrations of butenes to butanols are commercially important reactions as the products find several important industrial applications. Butanols have been deemed as second generation fuel components after ethanol. These butanols can be used as solvents or chemical intermediates for the production of corresponding ketones, esters, ethers, etc.
Butanols produced through typical bio-routes are not efficient and would not produce enough quantity to meet the demanding needs of the butanol market. Hydration, which is normally an acid catalyzed reaction, can be used, but it is costly. Because organic butenes have very low solubility in water, relatively strong acids are often required to achieve the desired kinetics to convert the butenes to alcohols. Other processes used to produce butanols are also expensive. For example, petrochemical routes to produce mixed butanols by hydroformation and hydrogenation from propylene and carbon monoxide are costly.
A conventional commercial method of production of secondary butyl alcohol includes using a two step processes in which the n-butenes are reacted with excess sulfuric acid (80%) to form the corresponding sulfate which is hydrolysed to SBA as follow:n-C4H8+H2SO4→2-C4H9OSO3H2-C4H9OSO3H+H2O→2-C4H9OH+H2SO4 During this process, the sulfuric acid becomes diluted to about 35% concentration by weight and must be re-concentrated before it can be reused. The advantage of the process is its high conversion rate. However, many additional problems are usually associated when using such liquid catalysts. Among the problems are separation and recovery of the catalyst, corrosion of equipment and installations, and formation of byproducts such as secondary butyl ether, isopropyl alcohol, C5-C8 hydrocarbons, and polymers. Some of these by-products complicate the purification of SBA.
Cationic exchange resins and zeolite are potentially important acid catalysts for olefin hydration. The cationic exchange resins are known to offer substantial rates in both polar and non-polar media. Attempts have been made to use sulfonated polystyrene resins cross linked with divinyl benzene as catalysts for the hydration of olefins such as propylene or butene. These types of catalyst systems offer several engineering benefits, such as ease in separation and provide a non-corrosive environment.
Butenes are sparingly soluble in water and form separated phases under the reaction conditions especially when butenes are used in a sufficiently large quantity. The butanol, being relatively non-polar, has a favorable distribution as a significant amount of butanols formed is expected to exist in the butene rich organic phase. Hence, simultaneous extraction during the course of the reactions might help in shifting the reversible reaction in the forward direction.
In spite of the currently available processes, there is no particularly effective route to produce mixed butanols through an economic route. Furthermore, the conversion rates of olefin hydration are low at less than 10% per pass.
A need exists for processes and systems that would allow for the direct catalytic hydration of alkenes to alcohols. It would also be beneficial if the processes and systems were inexpensive and provided a route to industrially useful alcohols and a convenient synthetic route for the synthesis of alcohols in general.
Additionally, there is a need for an additive or fuel that has improved octane rating as compared to gasoline and increased efficiency of combustion. There is a need for a fuel that reduces harmful emissions and airborne soot when combusted, either in neat form or as a fuel constituent.
There is also a need to provide a fuel of similar octane and BTU value to gasoline but without the use of tetraethyl lead, MTBE, methanol, ethanol, or MMT. It would also be desirable to provide a fuel additive that lowers the Reid Vapor Pressure of the fuel at least as well as, but without the use of, MTBE. It would be helpful if such fuels or additives would include mixed alcohols that are produced from mixed olefin streams.